[GRASS-dev] PostGIS manager for GRASS GIS

Mohit Kumar mohit.kumarug08 at students.iiit.ac.in
Thu Apr 5 02:56:19 EDT 2012

Hi all,
Shall I go with this PostGIS manager proposal and apply on melange 
Any further suggestions are welcome
Only one day is left to appply.

Thanks and regards,

On Wed, 04 Apr 2012 01:56:17 +0530, Mohit Kumar wrote:
> Hello Martin,
> Sorry couldn't reply earlier as I was stuck with some college work.
> On Mon, 2 Apr 2012 21:00:51 +0200, Martin Landa wrote:
>> Hi,
>> 2012/4/2 Mohit Kumar <mohit.kumarug08 at students.iiit.ac.in>:
>>>>> I am interested in making a PostGIS manager in GRASS as a GSoc 
>>>>> 2012 task.
>>>>> PyGreSQL is a python module that allows easy use of database 
>>>>> operation
>>>>> API
>>>>> from a pyhton script. So it will be like a wrapper over
>>>>> the database. This can be done using wxPython and will be OS 
>>>>> independent.
>>>>> Sorry to bug you all, but I am very much interested in developing 
>>>>> for
>>>>> GRASS.
>> [...]
>>>> there is new development ongoing for this in GRASS 7, perhaps a 
>>>> good
>>>> moment to integrate a manager. Maybe Martin has some insights for
>>>> us over the next days.
>>> Its good to know that development is ongoing for this in GRASS, I 
>>> sincerely
>>> want to work on this as my GSoc task.
>> the current PostGIS-related development in G7 is not much related to
>> this idea. The vector engine in G7 is currently able to read PostGIS
>> geometry data natively without any abstract level (like 
>> OGR-PostgreSQL
>> driver). Also write support has been recently implemented. The 
>> current
>> implementation is focused on simple feature access, GRASS builds a
>> pseudo-like topology as for OGR links (see v.external). At this 
>> moment
>> I am working on PostGIS topology support in GRASS.
>>> I have made a brief idea for the manager. The following are the 
>>> various
>>> modules of the manager
>>> 1. Setup connection : This module will set up the connection with 
>>> the remote
>>> database. It will take the input parameters from user and pass them 
>>> to a
>>> connection string. After the connection has been established, the 
>>> user will
>>> be shown the various tables(maps) that are stored and other 
>>> information
>>> about the database and the connection
>> This is already available in wxGUI [1]. Of course there is always a
>> space for any kind of improvements. But basically it's already 
>> there,
>> to add widgets for entering username and password is quite easy 
>> task.
>>> 2. View and edit data : This will display the data of the table in 
>>> a window
>>> frame. One can view the map and modify the table values or the 
>>> attributes.
>> Also possible in current wxGUI [2]. You just create a link using
>> `v.external` and display the map in the map canvas as normal GRASS
>> vector map. Also direct OGR access [3] is possible (no links,
>> pseudo-topology built on the fly)
>>> 3. Import to GRASS Data : This gives the user an option to save the 
>>> data in
>>> Grass format for further processing/analysis of the data. This also 
>>> gives
>>> user an option to discard the data which is of no use.
>> Possible with `v.in.ogr`. Simple wrapper based `v.in.ogr` for
>> importing PostGIS is already there [4].
>>> 4. Execute PostGis functions (geometry processing)on database and 
>>> save
>>> output in grass data format.
>> This could be improvement.
>>> 5. SQL interface : This provides the advanced user to modify the 
>>> database by
>>> use of direct SQL commands on the database.
>>> 6. Export GRASS data to PostGIS data : Convert the Grass Data to 
>>> SQL
>>> database. First convert the Grass data to Esri Shapefile(.shp) 
>>> using OGR and
>>> then converting that data to SQL database (shape2sql).
>> Why?? You can export data directly using `v.out.ogr` [5]. No need 
>> for
>> Shapefiles, that's bad idea.
>>> 7. Projection support : I was also thinking of adding projection 
>>> support to
>>> the manager.
>> In which sense, do you mean on-the fly re-projection (ST_transform)?
>> Martin
>> [1]
>> http://grass.osgeo.org/wiki/Working_with_external_data_in_GRASS_7#Using_wxGUI
>> [2]
>> http://grass.osgeo.org/wiki/Working_with_external_data_in_GRASS_7#Digitize_OGR_layer_using_wxGUI
>> [3]
>> http://grass.osgeo.org/wiki/Working_with_external_data_in_GRASS_7#Direct_access_to_external_data
>> [4] http://grass.osgeo.org/wiki/PostGIS#Import_into_GRASS
>> [5] http://grass.osgeo.org/wiki/PostGIS#Export_to_PostGIS
> Thanks for your feedback.
> I know that various modules are possible in GRASS wxGUI. I want to
> integrate them all and provide a direct interface for them. Regarding
> data Export I was thinking about 'v.out.ogr' only.
> And I was talking about on-the fly re-projection. The projection
> tables can be stored in which ever way the user wants.
> What more would you like to add to the current idea to make it worth
> for a GSOC proposal?
> Looking forward to your support.
> Regards,
> Mohit Kumar (mohitkharb on irc)
> Lab For Spatial Informatics
> International Institute of Information and Technology
> Hyderabad, India
> +91-970-3840-175
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Mohit Kumar (mohitkharb on irc)
Lab For Spatial Informatics
International Institute of Information and Technology
Hyderabad, India

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